Fuel system for gas-turbine engines



Mamh 1954 K. R. DAVIES ET AL 7 FUEL SYSTEM FOR GAS-TURBINE ENGINES FiledOct. 20, 1949 7 Sheets-Sheet l 117 PECIPROCATINO- AWE Q121 FUEL PUMP IluvlnToI-S KPJDAWE: ac. HeRBS J 1 wMMWR -I March 2, 1954 K. R. DAVIES ETAL 7 FUEL SYSTEM FOR GAS-TURBINE ENGINES I Filed Oct. 20, 1949 '7Sheets-Sheet 2 INVINTQIS K; R. DAVIE5 Q: Heass-rm-r-r a wakawm March 2,1954 K. R. DAVIES ET AL 2,670,

- FUEL SYSTEM FOR GAS-TURBINE ENGINES Filed Oct. 20, 1949 7 Sheets-Sheet4 INVENTORS k. R. Dunks 4; means-n11 Malrch 2, 1954 DAVIES ETAL2,670,599

FUEL SYSTEM FOR GAS-TURBINE ENGINES Fild Oct. 20, 1949 7 Sheets-Sheet 7INVKNT Patented Mar. 2, 1954 FUEL, SYSTEMFOR GAS-TURBINE ENGINESKenneth- Roy Davies, Ockbrook, and Karl'Herbstritt, Chellaston,England,assignors to Rolls-.. Royce. Limited, Derby, England; aBritishcom-.

Application 0131201381120, 1949,. Serial No. 122,498

Claimspriority, application .Great Britain' October 29, 19.48

(Cl. Gib-39.28)

2,4 Claims. 1

This invention relates turbine engines ofthe kind comprising governormeans sensitive to the rotational speed of the engine and having aselectively variable speed datum, said governor means being operative tocontrol the fuel supply to theengine to maintain a speed selected inaccordanceiwith, thesetting of .the variable datum.

It; is desirable in systems of this kind to providemeansforlimiting themaximum fuel flow obtainable during transient. acceleration conditions,andhitherto the maximum obtainable fuel fiow during, theseconditions-has been determined in amanner; such that the maximum fuelflow is substantially proportional to engine rotational- V bine, and maypossibly cause the flame to be extinguished. Overfuelling may-also causeunde sirable characteristics in the running of the en-. gine, such assurgeconditions in the compressor.

Accordingly, one object of the present inven tion seeks to provide meanswhereby the maximum fuel flow to the engine during transient,

acceleration conditions can be controlled in a desired'manner;

The invention can beapplied to fuel systems for gasturbine engines, ofthe type which'inelude a mechanism hereafter referred to as hydraulicgovernor means comprising'a hydraulic'pump of substantially fixedvolumetric capacity driven at a speed proportional to engine speedand'passing liquid through restricting orifice means, the pressure dropacross said restricting orifice means being applied to a pressureresponsive device. The pressure responsive means may be connectedtoeffect variation of fuel delivered to the engine, thus to maintain anengine rotational speed selected by adjustment of the area of'therestricting orifice means or by adjustment of a resilient load operatingon the pressure responsive device, or by adjustment of both;

Another object of the invention is to provide such a system with meanswhich is effective to permit an increase of the ratio of maximumpermissible flow to engine speed during a transient acceleration when apreselected value of an engineoperating-variable is reached:

to-fuel systems'vfor. gas.

One, important application of-our present invention is to a fuel systemfor a gas turbineengine, such as we have described; in our co-pending-U. S: application tNo. 87,696, filed April 15', 1949,- whichcomprises-a first hydraulic governor means which isarranged todefine-for eachrotational speed; of the engine,- a preselected maximumpermissible fuel flow to the engine in ex cess of engine requirementsforsteady running at each such speed, and a-second hydraulic-governormeans having a variable datum, which second governor means is arrangedto reduce the fuel supply from such maximum available fuel, supplyaccording toa selected'datum setting of the, variable datum of thesecond hydraulic governor means.

Embodiments of the, invention are diagrammaticallyillustrated in theaccompanying drawings-inlwhich:

Figure 1" illustrates a fuel system suitable for a gas-turbine aircraftengine, which is functionally similar to those described in ourcopending United States application Serial No.

Figure 1A: illustrates a modification of the fuel system illustrated inFigure 1;

Figures 2A and 2B illustrate stop mechanism forv adjusting maximumobtainable fuel flow, thearrangement of Figurue 2B'showing asimplification which is incorporated in Figure 1;

Figures 3A and 3B are diagrams plottinglfuel flow (F) against rotationalspeed (N) illustrating the functioning of the invention;

Figures 4A and 4B illustrate a modification of thearrangements shown inFigures 2A, 2B;

Figure 5 shows a modification of the arrangement shown in Figure 2B foruse with an alternative formof' engine control, and

Figure 6 illustrates a stop mechanism which functions in a differentmanner.

Figure 7 is a diagram plotting 'fuel flow (F) against rotational speed(N) illustrating the functioning of-the mechanism shown in Figure 6.

Figure 8 illustrates a stop mechanism which functions inyet anothermanner. I

Figure 9 illustrates modifications in the hydrau lic governor flowsystem shown in Figure 1..

Referring to Figure 1, thefuel, system corn-v prises a main fuel pumpIII! e. g. of the reciprocating multi-plunger kind, the volumetric capacity of which can be varied by means of a piston HI operating throughlever H2. Fuel enters the pump l-lil through suction pipe H3, whichincludes a manually operated low pressure, shut-oil cock H51 A fuel"supply tank is diagrammatically illustrated at H6. The fuel pumppressure delivery pipe is shown at I I1, from which pipe a pipeline II8communicates with the cylinder in which the piston III operates to loadthe latter in the sense of reduction of the stroke of the pump. Thepiston is loaded in the opposite sense by means of a spring H9 and alsoby hydraulic pressure supplied through ducting I23 from the pipeline I39delivering to the engine fuel injectors, one of the latter being shownat 12 I. This arrangement provides for a predetermined pressuredifference between the pressure of the pump discharge and that at thefuel injectors.

In addition to the variable delivery fuel pump IIIl there is a furtherpump I22 of the gear type which is driven by the engine at a speedproportional to that of the engine. As shown this latter pump isconveniently driven by the engine drive shaft I22A, which also drivesthe fuel pump H6. The pump I22 which is of substantially constantvolumetric capacity, draws fuel from the supply pipe H3 through thepipeline I 23, and delivers through discharge conduit I24. The flowthrough the pump is substantially directly proportional to the enginerotational speed. This flow is used in the hydraulic governing systems,passing through a fixed restriction I to a variable restriction I12. Theflow is returned by pipeline I26 to the fuel suction pipe II 3. Thevariable restriction I12 includes a valve element I13 adjusted by meansof a control lever I14 which control lever constitutes thespeed-selecting means for the engine. A relief valve 250 may beassociated with the variable restriction [12 to by-pass flow past itwhen a predetermined maximum pressure drop is reached. Such a reliefvalve will avoid an excessive pressure drop arising for example when thelever I14 is operated rapidly to close the restriction I12 to reduceengine speed.

It will be appreciatedthat since the hydraulic delivery flow of the pumpI22 is substantially proportional to the engine rotational speed, andthe restriction I 25 is fixed in size, a pressure drop arises acrossthis orifice, which is proportional approximately to the square of theengine rotational speed. This pressure drop is applied to the flexiblediaphragm I29, the pressure upstream of the orifice I25 being introducedby pressure tapping I33 (branching from the discharge conduit I24) intochamber I3I and the pressure down- Stream of the restriction beingintroduced by pressure tapping 189 into chamber I32. The diaphragm I29is connected to a rod I33 which operates a slide valve I34, arranged toco-operate with a valve port I35 at the delivery end of the fue1 supplypipe II 1. The slide valve I34 thus controls the flow from the supplypipe I I1 into an intermediate pressure chamber I36. The pressure inthis chamber operates on a further diaphragm I31 which is connected tothe rod I33. the rod being continuous through the diaphragm I31. Thelatter is additionally loaded by the pressure existing in the pipeline39 through passageway I46 to chamber I 4|.

It will be appreciated that the slide valve I34 is controlled as toposition by the balance of the loads on the diaphragms I29 and I31. Theload on the diaphragm I29 is approximately proportional to the square ofthe engine rotational speed and the load on the diaphragm I31 isproportional to the pressure drop existing between the intermediatechamber I36 and the fuel supply pipe line I39 to injectors such as IN.

A second hydraulic governing means is provided for controlling a furtherslide valve, indicated at I42, throttling the conduit between theintermediate chamber I35 and pipeline I33. This valve can be moved intwo senses, namely in rotational movement and in axial movement,respectively by an altitude sensitive device and by the pressuresensitive device of the second hydraulic governing means. The pressuresensitive device of the second hydraulic governing means comprises adiaphragm I43 which is subjected to the pressure drop across thevariable restriction I12, the pressure on the upstream side of thisrestriction being communicated through pressure tapping IBSA fromchamber I32, to the chamber I45, whilst pressure downstream of theorifice is communicated by passageway I9I to chamber I46. The diaphragmI43 is additionally loaded by means of a spring I81. Movement of thediaphragm I43 is transmitted to the slide valve I 42 through a push-pullrod I49.

In the rotational sense of movement the valve I42 is controlled by meansof an altitude sensitive capsule I58 accommodated within chamber I59which chamber is subjected to atmospheric pressure through connectionI60. The capsule is of the kind which expands axially as the result ofreduction of atmospheric pressure to which it is subjected. Axialexpansion thereof is transmitted by a servo device to a sliding rackmember 251) which carries a servo piston I55. The rack member 266engages a pinion 2M carried on shaft 202, and having crosshead 263engaging the valve I42 in an axially directed slot. The arrangement issuch that upward movement of the piston I55 results in rotation of thevalve I42 in the sense of closure, whilst downward movement of thepiston I55 results in movement in the sense of opening. A torsion spring204 biasses the piston I55 in the downward sense, i. e. in the sense ofopening the valve I42. The piston I55 is moved in the sense of closingthe valve, i. e. upwards, by servo pressure liquid which is derivedthrough passageway I62 from the fuel pressure supply pipe H1. Thepressure liquid enters the cylinder space I54 through restricted orificeI63 and a plunger rod I51 connected to the evacuated capsule I58operates as a valve controlling the flow of pressure liquid throughpassage I56 extending through the piston I55. The pressure on the upperside of the piston I55 is that existing in the intermediate chamber I36,and is thus of a lower value than that existing in the fuel supply pipeII1 so that, in operation, the area of the restricted orifice I53 iscorrelated with the area of the passageway I56, valved by the rod I51,to maintain balance of hydraulic and other loads of the piston. Thus ifthe capsule expands, the rod I51 closes the passageway I56 resulting ina build up of servo pressure causing the piston to move upwards andadjust the setting of the slide valve I42 in the sense of closure.Contraction of the capsule I58 opens the passageway I55 tending toequalize pressure on both sides of the piston I55 when the slide valveI42 moves in the sense of opening under the influence of the spring 204to follow up the movement to the rod I51.

The fuel system also includes a high pressure shut-ofi-cock I53incorporated in the fuel supply pipeline I39, used in shutting down ofthe engine. In addition, as illustrated, an emergency changeover valve205 is provided which can be operated by control lever 205A to isolatethe hydraulic governor control system described.

emergency manual fuel throttle 208; operated by lever 206A, can thenbeused to control the fuel. deliveryfrom the fuel pressure supply pipe 1'through branch II'1A to chamber 201'. The latter communicates with thefuel delivery pipeline I33-to fuel nozzles I2I. This partof the systemis solely for emergency operation in the event of failure of thehydraulic governor control.

The fuel system so far described is in accordance with the invention ofour prior U. S; ap plication Serial No. 87,696 and its functioning issimilar to the principles outlined in the specification of thatapplication. Thus the valve I42 is incorporated to modify the flow fromthe intermediate chamber I36 appropriate for the running condition ofthe engine as selected by the positioning of the lever I14 to define thearea of the restricting orifice 12. The slide valve I42 is formed withports I56 of rectangular form co-operating with the ports I61 at theinlet to the passageway I39 delivering fuel to the fuel injectors I 2|.The arrangement is such that axial movement of the valve to the leftresults in reduction of the port areas at I66, whilst'rotationalmovement of the valve arising from expansion of the capsule I58 alsocauses reduction of the port areas.

The restriction afforded by the ports I66 is increased when the secondhydraulic governor,

operating through diaphragm I43, senses an engine speed'in excess ofthat selected by a setting of the lever I14, i. e. when the pressuredrop between chambers I45 and I43 exerts a load overcoming the springloading I81. Alternatively, if the hydraulic governor senses a speedwhich is less than that selected by the setting of the lever I14, i. e.when the load'exerted by the pressure drop between chambers I45 and I46is overcome by the spring I81, the valve I42 will move to the right soas to increase the port areas I66 and thus reduce the restriction tofuel flowbetween chamber I36 and delivery pipeline I39.

The pressure difference between the delivery pipeline I39 and chamberI35 is however main.- tained to be substantially proportional to thesquare of the engine rotational. speed, this pres sure difference beingdetermined, by balance of the hydraulic loadings on the diaphragms I29and I31.

Neglecting variations in altitude, when the lever I14 is rapidly movedto reduce the restriction afiorded' by a restricting orifice I12, thevalve 2 moves to a maximum open position, and the maximum flow of fuelto the engineis then dependent upon the areas of ports 16.6, and on thepressure difference across them. This pressure diflerence is maintainedsubstantially propertional to the square of the engine rotational speed.therefore during transient acceleration conditions the maximum amount offuel which can pass to the injectors is proportional to the enginespeed, being defined by the maximumport areas I66.

Again neglecting variations in altitude, when the control lever I14 ismoved. tov increase the restriction afforded by the restricting orificeI12 the diaphragm I43 will be moved to the left against stop 208 to movethe valve I42 and reduce the port areas I66 to a minimum value. n

Thus during transient deceleration conditions the minimum flow of fuelwhich can pass to the engine is defined by th minimum. areas of' theports I86 and is substantially proportional to engine speed.

These maximum and minimum fuelflows; are, however,- in fact: alsomodified by the function.- ing of the capsule I58 which further reducesthe area of the ports I66 with increase of altitude.

It willbe appreciated that the main fuel pump need not b of the variablevolumetric kind but could be a constant volumetric capacity pump with aleak-off back to the fuel reservoir from the discharge pipe of the pump.Figure 1A illustrates such a system where it differs from the onedescribed above. In Figure 1A, the reference numeral It indicates afuel-supply tank, from which fuel is supplied through suction-pipe I3and a manually-operated low-pressure shutoff-cock I5 to theconstant-volume pump 22, which is the main fuel pump of the engine.-From the pump 22', the fuel passes through a discharge conduit I1 whichcontains a variable restriction 12, which includes a valve element 13adjustable by means of the control lever 13. The discharge conduit alsocontains a fixed restriction 25 between the pump 22 and the variablerestriction 12. Excess fuel, delivered by the pump 22, over thatrequired by the engine, is returned to the tank I6, through the reliefvalve 23.

The system described is connected to supply fuel to the fuel injectorsof the engine through a pair of hydraulic governors arranged asabovedescribed. The pressure tapping I3 is taken from the discharge conduitI1 upstream of the fixed restriction 25, the pressure tapping I89 istaken from between the fixed restriction 25' and variable restriction12, and the pressure tapping I9I is taken from downstream of thevariable restriction 12. Downstream of the relief valve 20 the dischargeconduit I1 is connected to the fuel delivery pipe H1.

The present invention provides automatically adjusted stop mechanism formodifying the maximum obtainable fuel flow to the engine duringtransient acceleration conditions. The functioning of one embodiment ofthe present invention may be more readily appreciated by reference tothe diagrammatic sketches Figures 2A and. 2B, and by reference tofurther descriptionv which follows of its application to the fuel systemshown in Figure 1.

Referring to Figure 2A the constant volume gear pump of the hydraulicgoverning systems is indicated at i22 receiving fuel from pipeline I23:and delivering it to discharge conduit Hi l, in which there is located afixed restriction I25 and variablerestriction I12. The slide valve I42is. operated. through rod I49 connected to diaphragm I43. The directionsof movement in sense; of opening and closing of the valve hi2 areindicated'by arrows on the sketch, and the items above referenced andothers as appropriate correspond to those similarly referenced inFigure 1. The pressure chamber I45 on one side ofthe diaphragm I43 isloaded through pressure tappings I83 and I 83A by the pressure on theupstream side of the variable restriction I12. The diaphragm I 33 isadditionally loaded on its other side by pressure in chamber I lfi fromthe downstream side of the variable restriction orifice I1-2throughpressure tapping ISEI, and further by'the spring N31. The axial movementof the valve I42 in the sense of opening is limited by means of a stopfit co-operating with abutment 2 carried by the diaphragm I33. It. willbe appreciated that the axial position of stop 2H1 defines the extent ofmaximum opening. of the vvalvev I42 due to. axial movement, this stopbeing supported on a rod 2 I2 which is continuous 7 through andconnected to diaphragm 2I3 and further connected to diaphragm 2 It. Themovement of diaphragm 2 I i is limited by stops 2 I and 2I8 respectivelyin chamber 2E? and chamber 2I8, these stops preferably being manuallyadjustable. The diaphragm 2M is loaded hydraulically in chamber 2 I1through pressure tapping I30A by the pressure existing on the up streamside of the fixed restriction I; the diaphragm H4 is also loaded on itsother side in chamber ZIB by the pressure existing on the downstreamside of the fixed restriction I25 through pressure tappings I83 and3913, and further by a spring 2I3.

Neglecting for the purpose of immediate explanation the interaction ofhydraulic loadings on diaphragm I43 and EM it will be appreciated theloading on thre spring 2I9 can be chosen so that at low engine speed,when the pressure drop across the restriction I25 is small, thediaphragm 2I4 is urged against the left hand stop 2I5 so that the stop2H1 will be in its extreme left hand position, thus restricting themaximum area of the port I65 in the slide valve I 42. At a preselectedengine rotational speed the pressure drop across the fixed restriction525 loads the diaphragm 2I4 to overcome the loading of the spring 2!!!moving the diaphragm 2M against the right hand stop 2 I 6, thus movingthe stop me so as to permit greater maximum area of the port I66. Thusit can be arranged that at a speed above a preselected value the maximumobtainable area of port I66 is increased as compared with the maximumobtainable area below the preselected speed.

It will be appreciated however that when the stop 2IIl is operativeagainst abutment 21 I, the loading on diaphragm I63 must be balancedsince it would affect the setting of the stop 2 II]. To this end a thirddiaphragm 2 I 3 is provided. Chamber 220 on one side of this diaphragmis loaded by hydraulic pressure derived from the upstream side of thevariable restriction I12 through pressure tappings I89 and I33C. On theother side diaphragm 2I3 is loaded by hydraulic pressure in chamber 22Iderived from the downstream side of the variable restriction I12 throughpressure tapping I9IA. Further a spring 222 additionally loads thediaphragm 2I3. The areas of the diaphragms 2I3 and M3 are the same; theloading of the springs I 31 and 222 are equal in a mean position; andthe pressure loadings on opposite sides, through pressure tappings I89A,IBHC, I9I, ISIA, are identical. Thus when the stop 2 IE) cooperates withthe abutment 2I I the loads on these two diaphragm assemblies I 53 and2I3 are balanced. This condition will arise during transientacceleration conditions when the stop 2 I It is operative to limit theopening movement of the valve I42, and during these conditions up to apreselected engine rotational speed defined by the loading on the spring2l2, the loading on the diaphragm 2I4 operates to define the position ofthe stop 2 I 0, the loadings on the diaphragms E43 and 2 I3 beinbalanced against each other.

A simplification of the system above described is shown in Figure 2B.Considering diaphragms 2I3 and 2I4 of Figure 2A, it will be seen thatchambers 218 and 228 are loaded by the same pressure, through pressuretappings IBtB and I890. This arises since, in the particulararrangement, the pressure on the downstream side of the fixedrestricting orifice I25 is identical with that existing on the upstreamside of the variable restricting orifice I12. If the diaphragm 2I3 hasthe same area as that of diaphragm 2I4 then these pressure loadings willcancel out, thus in eilect these two loadings can conveniently beomitted. This gives rise to the simplification shown in Figure 2B inwhich the constant volume governor pump I22 delivers to fixedrestriction I25 and thence through the variable restriction I12. Theslide valve I42 is again illustrated with port area I66, and isconnected by rod I49 with diaphragm I43 loaded in chamber I45 bypressure existing on the upstream side of the variable restriction I'I2through pressure tapping I89. The diaphragm I43 supports abutment 2cooperating with stop 2m carried on rod 2l2 connected to diaphragm 214.Diaphragm 2 I4 is loaded in chamber 2 I! by hydraulic pressure derivedfrom the upstream side of the fixed restriction I25 through pressuretapping I30A and its movement to the left is limited by stop 2I5.Intermediate the two diaphragms I43 and 2I4 is a common pressure chamberwith an internally directed Wall formation 223 providing fixed abutmentsfor diaphragm loading springs equivalent to those shown in Figure 2A;thus diaphragm I43 is loaded by spring I81 in chamber I it and diaphragmM4 is loaded by springs 2I9 and 222 in chamber 22I (common with chamberI43).

The wall formation 223 also supports an adjustable stop 2I3 limiting theright hand movement of diaphragm 2I4. A stop 208A on the rod I43(equivalent to stop 288 in chamber I46 in Figure 1) limits the movementof the valve I42 in the sense of reducing port area I66.

Functionally the arrangement of Figure 2B is similar to that of Figure2A, movement of diaphragm 2I4 adjusting the stop 2H] in axial locationand the hydraulic and spring loadings on diaphragm I 43 being balancedagainst equal loads when the stop 2H1 is operative against abutment 2II.

Referring again to Figure 1, the adjustable stop mechanismdiagrammatically illustrated in Figure 2B is associated with thediaphragm I43. Thus the spring I81 loads the diaphragm I43 in the senseof opening of the port areas Hit and the extent of opening is limited bythe stop 2H) co-operating with abutment 2 carried by diaphragm I43.There is further illustrated diaphragm 2I4 loaded by hydraulic pressurein chamber 22I (common with chamber I46), the pressure being derivedthrough pressure tapping I9I from the downstream side of the variablerestriction I12. This side of the diaphragm 2I4 is additionally loadedby springs 2I9 and 222. The inwardly extending wall 223 constitutesabutments for springs I81, 2I9 and 222. On its other side the diaphragm2 I4 is loaded by the hydraulic pressure existing in chamber 2i? whichpressure is derived through pressure tapping I33A, chamber I3I andpressure tapping I33 from the upstream side of the fixed restrictionI25. A selectively adjustable stop 2I5 limits the movement of thediaphragm 214 in the left hand sense, thus to define the amount by whichthe maximum openings by axial movement of port areas I66 is reduced atrotational speeds of the engine below that at which the pressure dropacross the dia phragm 2 I4 exceeds the loading of the spring 2 I 9.Additionally adjustable stop 2I5 defines the limit of the movement ofthe diaphragm 2| 4 to the right, thus to define the maximum area ofopening of the ports I66 which can be obtained.

During steady running conditions it will be appreciated that the stop2III will be inoperative, i. e. out of contact with the abutment 2H andthus the se ond overno wil rio uii norma out-on unotion Although notforming a feature of the pres.- ent invention, it should be mentionedthat the bleed orifice 209 between the fuel supply line I if! and i eediat cha b 3 b o i as ine the val e 1 i nc rat d to prov ders nr etsr mn d minimum-fuel flow fo d ing pur esilhe un t i o t s tem d sorih dinlay he m e r d app ec t d b re e en e o F ures 3A and BB. Thesefigures illustrate dioe a ti ally cur e p o n ue vflo F agai en ine rots ed N Fieure 3A indicates the curves for low altitude conditions,utilisin the ufli .0 d Figu 3 i lus ra curves h gh a tud c n t ons utiisi the .0, equivalent, for example, to the .cQnditions at 40,000 it.altitude.

Assum r t e pu ose of na i n tha in Figure 1 the capsule J58 does notoperate to move the .valve by rotation fromitslow altitude posi on n thed hr gm 2 l s d li -a ain t the adjustable ,Stop 2 L6, i. e.,so thatthestop 2H) permits a maximu rn opening of the port areas L6 h iax almemo toi t va ve heninfli ureBA s ig in s 0 As (Max) a d out M n sh r speel the max mu and m n mum low l nsslas d fin d by the first hyd aulio oorno O er d value 1.34 and he vina imum and m n mu a e o the valve portits obtaine to axial vmovement of the valve between the stop 219 and thestop 2.0.5. The line 0A0 (Max) indicates the maximum obtainable fuelflow for the low altitude position of the valve Hi2, i. e. the fuel flowobtained when'the valve M2 is fully open by axial movement, and the v lQe of this line at an point ind ca e the r i of maximum ohai ahle fuelnew o engin rotat nal speed at that poi t I o n O Au (Min indiootes thfuel now when the valve 1,4,2 is fully closed by axial movemen f e enine requ r men iuel lin er-i .ior a a -t n is -pro ul io e gine isindica e b t e .curve E ite andlies etw en 0 rho :(Max) and 0 .A0 (Min).

.111 Fieurefi s mil iv o 'lin s no (Max 0 A40 (Min) are shown, definedby the setting of the valve L42 after rotation by the pressure oapsule158 when subjected to pressure at high altitude, .e. g. 51 00 i The enin requi m n li e is indicated at EH40.

As described inou si -pendin .U- ap l atio S r alNo. 8 696, the n inesneedisise ested b m al ad ustment .of the variable restr ct o 12 theoperation of e second hy raul c govern r in such th hen the p sure d opac ss t is restrict o r aches th val at w ich theh raul il ading. on thediaphra m .1143 overeoines the spring loading 181, the valve [4'2 ismoved toreduoe henor a a 6B and thus reduce the fuel supply to theenginealonggovernor out-off lines- V' Yhe .-.intersecti n of two overn u-off li f two s lee e peeds isshown at N1 a d cut i t en n uir men ines's andiE as illu trated inFieures :3A an.d 3B- A sume that the n e spe dabilised a menu the contr l le er 1.1.4 is then aoidlvniov d t iope th ao the restrict on 1 2.11 orde to sel otlthe speed ivin t e inte seotonat N2 h l nm diate result o o nin oft er striotion H2 is .to reducethe pressure drop across this re ri tionsothat th va e L 2 i o enedhythospring I81 to give the maximum portareas at 1.65, a defined Jo the stopm and abutmen .21 Sti lassuin ne to the pu pose o exp anation, that thstop .2 isiloo t d to -,s v.e thernia inium between he 0 A0 (Max a d EB:F ure 3A and A40 Max) and Ro (Figure 3B) ndi ates the ex es u passin toth asneine d r n the trans ent cceler o cond tio the ase o c t in eng ns t s amount o excess fuel e ults in en in runninsioha asto i t os of anu de b atu e, whi h oanhe at ri uted o e elins. Suc r e ins may e ulinex in i o m u tion and/or urging of .theleompres sor of the engine.

h p e e invention vides by heoadiust-r ab top m an ociated it the d praem 1.43 pr i u l d sc ib r he edu tion of the ratio of maximumobtainable jiuel ilo e n a ona s ed a ne ds holowa preselected value.Thus the spring 219 urges the ia a m 21 4 to the l t t a just theston3110 providin m im port a e s 1B5, oh ainahle'by ax a move e o th a ve,which a ess than those giving the maximum flow lines 0 As (Max) and 0 A40 (Max).

T e m m f ow. es for th 'l oation o the s op 2 a is n whe the diaphra m2 4 a uts stop 2 nde he influ nce o the s rin "2& a e i di a d -Q D i urA and 0 i3 (Fieure BB which have a s a ler s e han ine O Ao.(Max) and 0A40 (Max) respectivelyand so indicate a smaller ratio of maximum fuelhow to engine rotational speed.

Wh n th en ine r ta i na .soeed re c a preselected value Na during thetransient acoelo io o dition th r ssu e o acros t fixed restrictingorifice I205 reaches a value such ha e s i loadi 219 is e o ieandtdiaphragm 2M starts to .move to the right to adj t e s p 2 h a eate onine o th p t a s J5 c rres ondin t th m x mum ob n b e flo lin 0 .A (Mx) Fi ure 3A an (Olen Ma (Fi ure 7.3.3) i thusnerini ted- Due to therating of spring 219 the ohangeover rom m xim flow lines :330 .OiBn '0and .0 VA a es p ao o e airsp ed ran e shown by it A in ant n us peeds ig in he ran e of .n t max mu fu l flow wi l .i o low hel ne shownJoining 0 Bo 0 13 0 an n Air M x 0 vA40 ax) sp ct vely, as i dic ted.-As will b s e a r du d va ue o th at of maximum obt i ab e fuel flow toeng ne rotaiona s ed durin the transien .aoo leration ondi i main ain dunti th rota ion speed ea hes N3 a t r wh sh i in ea es to .atain thevalue defined y he rnaximurni owii o 0 A0 (Max) and 0 A40 (Max). Foralchange o s eed sele d as betwee .N and N2 t xce s fue su p ie duringaoce a o is hyzthe.cr s-h oheda ea .It willvbe appr cia ed that. the syem, desc ibed with reference to Fi ur 1, the v lue of o n b preseloo e.h a su a le load n o sp ing 2 l 9 .in elat on to th -.ar.ea o the rstrict on "i --,and the no .th ro hroug urthe the slooeofithe maxim mewline, oinin 0 "h and 0 no iii lax) andisini l l that ioil. no.0 Bowith v1' A40 an be chos n .by th ap ropriate selecti n of th ratin o hesprin 1L A further variant of the arrangement shown in Figures gnan 2B il u ted FisuresA and iii In this cas th lo at on o th hir d ro oti n 125(an he variabl restrict on J12 in the :di oha s us rom th pump vare .re-

mam

versed as compared with the arrangement of Figures 2A and 2B. Thepressure drop across the variable restriction I12 is applied aspreviously to diaphragm I 43 by pressure tappin IB9A communicating withchamber I45 from the upstream side of the restriction I12, and bypressure tapping ISI communicating with chamber I46 from the downstreamside of the restriction I12. The diaphragm is additionally loaded byspring I81 in chamber I46 and carries abutment 2II co-operating with thestop 2H1. The latter is carried on the rod 2I2 continuous through andconnected to the diaphragm 2I3 and also connected to the diaphragm 2I4.The diaphragm 2I3 constitutes, as in the case of the arrangement shownin Figure 2A, a device for balancing the hydraulic loading on thediaphragm I 43 when the stop 2Ifl and abutment 2H interengage. To thisend the diaphragm 2I3 is loaded hydraulically through pressure tappingI9IA in chamber 22I and additionally by spring 222 in this chamber. Onits other side the diaphragm is loaded through pressure tapping I896 inchamber 226. The movement of the diaphragm 2I4 is limited by adjustablestops 2I5, 2I6, as in the case of the arrangement of Figure 2A, and thisdiaphragm is loaded in chamber 2I1 by the pressure on the upstream sideof the fixed restriction I25 through pressure tapping I9IC. On its otherside in chamber M8 the diaphragm is loaded by spring 2I9 and by thepressure on the downstream side of the fixed restriction I25 throughpressure tapping 230.

The functioning of the arrangement of Figure 4A is similar to thatdescribed in relation to Figure 2A, the stop 2I0 being adjusted bydiaphragm 2I4 so as to reduce the maximum value of the port area I66obtainable by axial movement of the valve I42 below a preselectedrotational speed and to permit increased maximum area obtainable byaxial movement of the valve I42 above the said preselected speed. Whilstthe stop 2I0 is operative against abutment 21! the hydraulic and springloads on diaphragms 2 I3 and I43 balance out.

The arrangement of Figure 4A can be simplified in a manner similar tothat of Figure 23, as shown in Figure 4B. It will be noted that thehydraulic loadings on the diaphragms 214 and U3 respectively (Figure 4A)in chambers 2I1 and 22I are identical. Thus if the areas of the twodiaphragms are the same these hydraulic loadings cancel out and canconveniently be omitted giving rise to simplification of Figure 4B.

The constant volume governor pump I22 delivers to the variablerestriction I12 and thence to the fixed restriction I25 in the dischargeconduit I26.

The slide valve I42 is again illustrated with port area I66, connectedby rod I46 with diaphragm I43. The latter is loaded in chamber I45 bythe pressure existing on the upstream side of the variable restrictionI12 through pressure tapping I89A. The diaphragm I43 supports abutment2II co-operating with stop 2Ill carried on rod 2I2 connected withdiaphragm 2I4. Diaphragm 2I4 is loaded in chamber 2I1 by hydraulicpressure derived from the upstream side of the variable restriction I 12through pressure tapping [89C and its movement to the left is limited bystop 2 I5.

The diaphragm 2 I4 is loaded in chamber 2 I8 by hydraulic pressurederived from the downstream side of the fixed restriction I25 throughpressure tapping 230. Diaphragm 2I4 is also loaded in chamber 2 I8 bysprings 222 and 2I9, equivalent to those shown in Figure 4A. Themovement of the diaphragm to th right is limited by preselectivelyadjustable stop 2I6. Further a stop 268B limits the right hand movementof the valve I42 in the sense of reducing the port area I66 to definethe minimum port area during deceleration conditions. Functionally thearrangement of Figure 4B is similar to that of Figure 4A, the movementof the diaphragm 214 adjusting the stop 2I0 in axial location and thehydraulic and spring loads on diaphragm I43 being balanced against equalloads when the stop 2 I 0 is operative against abutment 2 I I.

The arrangement of Figure 413 can conveniently be incorporated in thesystem of Figure l by locating the fixed restriction I25 on thedownstream side of the connection of pipeline I9I with pipeline I26.Thus referring to Figure 1, the connections I33 and I89 will be maderespectively to the upstream and downstream sides of the fixedrestriction I25 thus located. Th dividing wall 223 will extend intosealing engagement with the rod 2 I2 supporting the stop ZIIl toconstitute two distinct chambers 22! and I46. The interconnectingpassage I 36A will be deleted and separate hydraulic connections made tochambers 2 I1 and 22I (equivalent to chamber 2I8 in Figure 4B), theseconnections being respectively made to the upstream sid of the variablerestriction I12 and to the downstream side of the fixed restriction I25.In addition, the interconnecting passage I89A will be deleted and ahydraulic connection made to the upstream side of the variablerestriction.

As described in our co-pending U. S. application Serial No. 87,696, analternative method of selecting the engin speed is possible whichinvolves the selective adjustment of the load of the spring I81 on thediaphragm I43; the variable restriction I12 being replaced by anadditional fixed area restriction. Such a form of control may beadvantageous for certain engines and Figure 5 illustrates theapplication of maximum fuel flow stop adjusting mechanism to a system ofthis kind.

The arrangement of Figure 5 is immediately comparable with thearrangement of Figure 2B and may he arrived at through the process ofsimplification of th arrangement of Figure 2A. In Figure 5 the referencenumerals and major parts of the construction correspond throughout tothose of the arrangement of Figure 213, there being additionallyincorporated mechanism for selectively adjusting the loading on thespring I81 and simultaneously and comparably adjusting the load onspring 222. To this end the springs I81 and 222 bear against sleeves232, 332 which are slidably adjustable towards and away from thediaphragm 2 I4 and I43.

Sleeve 232 associated with the spring I81 slides on the abutment 2carried by diaphragm I43 and the sleeve 332 associated with spring 222slides on a collar supported by diaphragm 2I4. interposed between thetwo sleeves 232 and 332 is a rotatable cam 233 having arms contactingexterior plane surfaces of the sleeve. Selective rota tion of the cam bya suitable control lever adjusts the load on both springs I81 and 222simultaneously. In this manner the balance of the spring loads when thestop 2 I 0 engages the abutment 2I I is maintained.

It should be noted that the spring 2I9 is unafiected by the rotation ofthe cam 233, its abutment against radially inwardly extending wallcompressor.

":13 223 being flxed. Abutment 2 ISA, carried bythe diaphragm 21 4limits the *movement of the diaphragm zl l to the right andcorresponds-to the stop 2 I6 show-nin Figure 23.

-It will be appreciated that in the system described a'bove theadiustment oi the maximum fuel fiow stop takes place at a preselectedengine rotational speed. In addition, it is convenient .to use asdescribed the pressure drop which arises over a fixed restriction I 25in the stop "adjusting mechanism, this restriction being primarilyincorporated for the purposeof loading the diaphragm I29. Incertaincases a separate fixed restriction may be provided specificallyto produce thepressure drop operating the-stop adjusting mechanism.

Further,- the stop adjusting mechanism can be controlled according toother conditions associatedwith therunning ofthe engine. For example thechangeover-may be effected when a given'predetermined actual fuel flowto the en- 'gine isreached.

Apart of such a system is illustrated in Figure B and it will be seenthat it comprises a diaphragm arrangement as shown in Figure 2A. Howeverthe discharge conduit-I24 of the constant-volume pump I22does'not-contain a fixed "restriction, but instead a fixedrestriction-325 is containedin th 'fuel delivery 'pipe I39 and "islocated so that all the fuel flowing to the engine "passes through it.The-pressure drop across this fixed restriction-=32 5- is applied to thediaphragm -"2I4 bymeans of the pressure tappingsIwA and --I 89B.Elsewhere the-system is the same as that described with reference'to'Figure 2A, and the same reference numerals have been used toindicatethe corresponding parts.

Thesystem described with reference to Figure 6 will operate" so thatwhen a'predetermined fuel 'flow is reached thespring 2|9'is compressedto' increase the maximum permissible opening'of the -port=area I66.

Maximum obtainable fuel flow lines for such will compress the'loa'dingspring,thus permitting --in'creased ratio =of'maximum obtainable fuelflow to-engine rotational speed so that there is a =changeover to themaximum fuel flow lines 0 Ac-(Max), O-A2o (Max) andO A40 (Max).

For the three altitudes mentioned the maximum obtainable fuel flow 1. e.the actual fuel flow durin transient acceleration conditions, are: shownby I the curves 0 B0 A0, 0- B20 A20, 0 'BwAlo. 'With such anarrangement, the changeover is effected at'a R. P.'M. which increaseswith' altitude as indicated by No, N20, N40.

In other variants of the invention,'the"changeovermaylbe eiiected'when apredetermined com- --pressionratiois passed-through or when apredetermined absolute compressor discharge'pressure is attained orwhena predetermined compressor pressure rise isattained. A portion of'afuelsystem' in which changeover can be effected at such times isillustrated in Figure 8. 'Figure 8 shows a gas-turbine engine compris-'ing a compressor 400, combustion equipment MI and a turbine. 402.'having asrotor 140.3,driving. the The fuel supplied tothe engine ismeteredfin a device ias'described withzreferencezto Figure 1 whichincludes the-throttle valve M2. The setting of the throttle valve I42 isdetermined by the flexible diaphragm I43, subjected to :thepressuredifierence across a variable restriction cltinthe dischargeconduit #26 vof aconstant volumepump s22 driven at a speed proportionalto the speed of the turbine. "This pressure .difference loads thediaphragm I43 against theactionof aspring 181.

In this embodiment, the maximum area :to whichthe throttle valve I42 canbe opened, is limited when the compression ratio or compressor dischargepressure is below ,a selected value, :by interengagement of the stop 4H)and co-operatingabutment MI. The. stop iIIl is carried on a rod 41:2which passes throughand is engaged with a diaphragm M3, tohave slidingengagement with the lever 4%. The diaphragmew is subjected to thepressure difference across the variable restriction W2, is of thesamearea as the diaphragm I48, and is loaded by the spring 422 which isof the same rate as and applies the same load as the spring s81. Thus itwill be seen that when the stop M0 and co-operating abutment lII areengaged, the loads on the rod 4L2 from the abutment ll I are balanced bythe loads on it from the diaphragm M3, and the position .ofthestop 45Bis dependent solely on the position of the lever set.

The lever ist pivots about a fixed fulcrum 445 and has two evacuatedcapsules 429,152! pivotally connected to it, one on either side of thefulcrum.

The capsule s2! is contained ina chamber All which is connected, througha pressuretapping 439, with thedischarge of the compressorlllll.

The capsule 42b is contained in a chamber M8 which, in the figure, isconnected through pressure tapping see, and pressure tapping 59 I, tothe inlet of the compressor ltil.

The lever 44% is free to rotate about its fulcrum445 between twoadjustable stops M5, 4I6, and itwill beseen that, the lever cat will beurged anti-clockwise by: the pressure acting on the .capsule 428 untilthe compression ratio attains .a selected value dependent on the ratioof the distance along the lever arm between the fulcrum and theconnection to capsule 429, and between the fulcrum and the connection tocapsule AZI respectively. At this value the moment applied to the leverbythe capsule 32i balances that applied to it by the capsule are. Onincrease of compression ratio, the lever Mt will move from the stop M5towards thestop Mt.

It will be appreciated that if only the evacuated .capsule142l isemployed in chamber All, the lever 4 46 will move from the stop t Itwhen the absolute discharge pressure of the compressor 4% reaches afirst selected value and will come up against the stop AIB when itreaches a second greaterselected value dependent on the rate of thecap-.sule 42I.

Thus, since the-stopdit moves with the. lever 446, the throttle valvewill be limited inopening movement to a first position, untilhthecompression ratio or discharge pressure reache aselected value and willthereafterbe able to open togreater extent as .the'levert lfi moves'fromthe stop f4 I 5.

.Another embodiment by means of whicha changeover may be efifected whena predeter- .mined compressor pressure rise ispassed through will'bedescribedwith reference toIFigure 2A. In this embodiment, the pipe linesItliA and I893 are omitted. Chamber 2I,'I.is connected to :the dischargepressure of the compressor and chain-- her 2|8 is connected to the inletpressure of the compressor. It will thus be seen that the diaphragm 214is loaded by a pressure proportional to the difference between thecompressor delivery pressure and the compressor inlet pressure, inopposition to the load of the spring 219. The remainder of the system isexactly as described with relation to Figure 2A.

In operation, when the compressor pressure rise exceeds the selectedvalue, the load on the diaphragm 215 due to the difference between thecompressor delivery pressure and the compressor inlet pressure overcomesthe load due to the spring M9 and moves the stop 2!!! to the right inthe figure, thus increasing the maximum area to which the throttle valveI42 may be opened. When the stop 2H) and the -012 crating abutment 21!are engaged, the loads on the rod 2l2 due to the diaphragm I43 arebalanced by those transmitted to the rod by the diaphragm 213, and theposition of the stop 21a is dependent solely on the position of thediaphragm 2.

In addition, the fuel system may incorporate a temperature controlsystem of known or convenient kind, the function of such temperaturecontrol system being to ensure that the temperature of gases flowingthrough the turbine system does not exceed a predetermined value. Forexample, a temperature sensitive element such as a thermocouple orresistance thermometer situated in the exhaust duct of the engine mayprovide an output when a selected temperature is exceeded, which outputis amplified through a suitable electronic amplifier to actuate a fuelcontrol means reducing the supply of fuel to the engine. In applyingsuch a system to the arrangement described with reference to Figure 1,the output from the amplifier may be used as shown in Figure 9 to closean auxiliary throttle 235 when a predetermined temperature is reached.An auxiliary throttle 235 located in the position indicated modifies thevariable restriction [12, which has additionally a relief valvebypassing flow past it to avoid excessive pressure drop arising when therestriction is closed by rapid movement of the control lever I'M.

Figure 9 also illustrates a restriction [25A equivalent to the fixedrestriction H in the system of Figure 1, having an associated ambienttemperature control capsule 235. The purpose of this capsule is tomodify the pressure drop across the restriction I in accordance with theambient temperature, by increasing the area of the restriction withreduction of temperature and vice-versa. This pressure drop operating onthe diaphragm I29 defines the pressure differential between chamber Iand delivery pipeline I39, so that with reduced temperature thispressure drop is increased thus increasing the fuel flow to the engine.In combination with the pressure capsule I58 the ambient temperaturecapsule 236 controls the fuel flow correctly in accordance with thedensity of the ambient atmosphere or compressor intake air, where thecapsules are arranged to sense pressure and temperature at the airintake.

The systems described in relation to Figures 1 and 2 are very suitablefor use with gas-turbine engines for aircraft propulsion in whichpropulsive thrust is derived from the high exit velocity of an exhaustgas stream, the rotational speed of a compressor and turbine rotorassembly being determined by the fuel supply to the engine. Theinvention is also applicable to gasturbine engines in which externalshaft power is derived, and utilized for example in driving an airscrewor ducted fan. In such cases it is preferably arranged that the loadimposed by the airscrew is adjusted by means of a temperature controlsystem such as outlined above, to avoid excessive temperature arising inthe turbine.

In the above description and in the appended claims, it is to beunderstood that a diaphragm may be replaced by a piston tight in acylinder or by a bellows and the word diaphragm should be read toinclude a piston or the end-wall of a bellows.

We claim:

1. For use in a throttle-valve controlled fuelsupply system ingas-turbine engines, a stop cooperating with such system which stopforms a restraint on the degree of opening movement of the valve and isadjustable relative to the valve, a constant volume pump driven by theengine at a speed proportional to that of the engine, adischarge-conduit from said pump, a fixed restriction in said conduit, amotor for adjusting said stop comprising a movable diaphragm andchambers to opposite sides of said diaphragm in communication separatelywith said discharge conduit at opposite sides of said restrictionwhereby the diaphragm is sensitive to the pressure drop across saidrestriction with the high pressure side of the restriction acting toinfluence the diaphragm in moving the stop to diminish the restraint onthe opening movement of said valve, and a loading device for loadingsaid diaphragm with a selected load biasing the diaphragm to an oppositemovement in which said stop is adjusted to a position of greaterrestraint on the degree of opening movement of the valve.

2. A gas-turbine engine having a rotor and a fuel-supply system; aconduit in said system; a throttle valve for controlling the fuel flowthrough said conduit; a stop movable relative to said throttle valveinto and out of a position, and operative at least in said position, tolimit the opening movement of said throttle valve; means sensitive to aselected value of an operating variable which is dependent at least inpart on the speed of the engine and including a member which movesthrough a given location when said selected value is passed through, andan operative connection between said member and said stop whereby saidstop is moved from said position when said member passes through saidgiven location due to increase of speed, and is moved to said positionwhen said member passes through said given location due to decrease ofspeed.

3. A gas-turbine engine having a rotor and a fuel-supply system; aconduit in said system; a throttle valve for controlling the fuel flowthrough said conduit; a stop movable relative to said throttle valveinto and out of a position and operative at least in said position tolimit the opening movement of said throttle valve; means sensitive to aselected value of the speed of said rotor; and including a member whichmoves through a given location when said selected value is passedthrough, and an operative connection between said member and said stopwhereby said stop is moved from said position when said member passesthrough said given location due to increase of speed, and is moved tosaid position when said member passes through said given location due todecrease of speed.

4. A gas-turbine engine having a compressor,

17 a rotor, and a fuel-supply system; a. conduit in said system; athrottle valve for controlling the fuel flow through said conduit; isstop movable relative to said throttle valve into. and out of a positionand operative at least in said position to limit the opening movement ofsaid throttle valve; means sensitive to a selected value of the pressureratio between the intake and delivery of said compressor; and includinga member which moves through a given location when said selected valueis passed through, and an operative connection between said member andsaid stop whereby said stop is moved from said position when said memberpasses through saidgiven location due to increase of said pressureratio, and is moved to said position when said member passes throughsaid given location due to decrease of said pressure ratio.

5. A gas-turbine engine having a compressor, a rotor, and a fuel-supplysystem; aconduit in said system; a throttle valve for controlling thefuel flow through said conduit; a stop movable relative to said throttlevalve into and out of a position, and operative at. least insaidposition to limit the opening movement of saidthrottle valve; meanssensitive to a selected value of the absolute delivery pressure of saidcompressor; and including a member which movesthrough a given locationwhen said selected value ispassed through, and an operative connectionbetween said member and said stop whereby said stop is moved from saidposition when said member passes throughsaid given location due toincrease of said absolute delivery pressure, and is, moved to, saidposition whensaijdj member passes through said given location. due todecrease of said absolute delivery pressure...

6... A gas-turbine en ine having a compressor, a. rotor,. and a.fuel-supply system, a conduit in said, system; a. throttle valve forcontrollingthe fuel flow through. said, conduit; a stop movable relativeto said throttle valve into and out of a position, and operative at.least in said position to limit the opening. movement. of said throttlevalve; means sensitive to a selected value of the pressure rise of said.compressor; and includinga member which moves throu h a given locationwhen said selected. value is passed through, and an operative connectionbetween said member and said stop whereby said stop is. moved from saidposition when said member passes through said given location clue toincrease of. Said pressure rise, and is moved to said position when saidmember passes through. said. given location due to decrease of said.pressure, rise.

7. A gas-turbine engine having, a rotor and a fuel-supply system;aconduitinsaid; system; a throttle valve for controllingthe fuel-flowthrough said conduit; a stop movable relative to said throttle valveinto and. out of a. position. and operative at least in said position tolimit. the opening movement of said throttle valve; means sensitive to aselected value of. the actual fuel flow to the engine; and including a.member a throttle valve for controlling the fuel flow through saidconduit; a stop movable relative to said throttle valve into and out ofa position and operative at least in said position to limit the openingmovement of said throttle valve; a constant volume pump; a drivingconnection between said pump and said rotor, whereby said pump is drivenat a speed proportional to that of said rotor; a discharge-conduit fromsaid pump; a fixed restriction in said discharge-conduit; a firstchamber; a second chamber; a flexible diaphragm dividing said firstchamber from said second chamber and connected to said stop; a firstpressure tapping from said discharge-conduit upstream of fixedrestriction to said first chamber and a second pressure tapping fromsaid discharge-conduit downstream of said fixed restriction to saidsecond chamber whereby said diaphragm is loaded by a resultant pressureload proportional to the pressure drop across said fixed restriction;and a loading device arranged to load said diaphragm with a selectedload towards said first chamber; whereby said stop moves out of saidposition when said resultant pressure load exceeds said selected loadand into said position when the resultant pressure load falls below saidselected load..

9. A gas-turbine engine having a rotor and a fuel-supply system; aconduit in said system; a throttle valve for controlling the fuel flowthrough said conduit; a stop movable relative to said throttle valveinto and out of a position and operative at least in said position tolimit the opening movement of said throttle valve; a constant volumepump; a driving connection between said pump and said rotor, wherebysaid pump is driven at a speed proportional to that of said rotor; adischarge-conduit from said pump; a fixed restriction in saiddischarge-conduit; a first chamber; a second chamber; a flexiblediaphragm dividing said first chamber from said second chamber andconnected to said stop; a first pressure tapping from saiddischarge-conduit upstream of said fixed restriction to said firstchamber and a second pressure tapping from said discharge-conduitdownstream of said first restriction to said second chamber whereby saiddiaphragm is loaded by a resultant pressure load proportional to thepressure drop across said fixed restriction; and a loading devicearranged to load said diaphragm with a selected load towards said firstchamber; where'- by said stop moves out of said position when saidresultant pressure load exceeds said selected load and into saidposition when the resultant pressure load falls'below said selectedload, and whereby the opening load applied to said throttle valve istransmitted to said diaphragm; and means to apply to said diaphragm aload equal magni tude and opposite in direction to said opening load.

1-0.. A. gas-turbine engine having a rotor and a fuel-supply system; aconduit in said system;

a throttle valve for controlling the fuel flow through said conduit; astop movable relative to said throttle valve. into and out of'a positionand operative at least in. said position to limit the opening movementof sai'dithrottl'e valve; a supply-conduit in said system located topass the actual fuel supplied to the engine; a fixed restriction in saidsupply-conduit; a first chamber; a second chamber; a flexible diaphragmdividing said first chamber from said second chamber and connected to]said stop; a'first pressure tapping from said supply=conduit-'upstreamof said fixed restriction to said first chamber and a second pressuretapping from said supply-conduit downstream of said fixed restriction tosaid second chamber whereby said diaphragm is loaded by a resultantpressure load proportional to the pressure drop across said fixedrestriction; and a loading device arranged to load said diaphragm with aselected load towards said first chamber; whereby said stop moves out ofsaid position when said resultant pressure load exceeds said selectedload and into said position when the resultant pressure load falls belowsaid selected load.

11. A gas-turbine engine having a rotor and a fuel-supply system; aconduit in said system; a throttle valve for controlling the fuel fiowthrough said conduit; a stop movable relative to said throttle valveinto and out of a position and operative at least in said position tolimit the opening movement of said throttle valve; a supply-conduit insaid system located to pass the actual fuel supplied to the engine; afixed restriction in said supply-conduit; a first chamber; a secondchamber; a flexible diaphragm dividing said first chamber from saidsecond chamber and connected to said stop; a first pressure tapping fromsaid supply-conduit upstream of said fixed restriction to said firstchamber and a second pressure tapping from supply-conduit downstream ofsaid fixed restriction to said second chamber whereby said diaphragm isloaded by a resultant pressure load proportional to the pressure dropacross said fixed restriction; and a loading device arranged to loadsaid dia phragm with a selected load towards said chamber; whereby saidstop moves out of said position when said resultant pressure loadexceeds said selected load and into said position when the resultantpressure load falls below said selected load, and whereby the openingload applied to said throttle is transmitted to said diaphragm; andmeans to apply to said diaphragm a load equal in magnitude and oppositein direction to said opening load.

12. A gas-turbine engine having a compressor, and a fuel-supply system;a conduit in said system; a throttle valve for controlling the fuel flowthrough said conduit; a stop movable relative to said throttle valveinto and out of a position and operative at least in said position tolimit the opening movement of said throttle valve; a first chamber; anevacuated second chamber; a flexible diaphragm dividing said firstchamber from said second chamber and connected to said stop; apressure-tapping from the discharge of said compressor to said firstchamber whereby said diaphragm is loaded by a resultant pressure loadproportional to the absolute discharge pressure of said compressor; anda loading device arranged to load said diaphragm with a selected loadtowards said first chamber; whereby said stop moves out of said positionwhen said resultant pressure load exceeds said selected load and intosaid position when the resultant pressure load falls below said selectedload.

13. A gas-turbine engine having a compressor, and a fuel-supply system;a conduit in said system; a throttle valve for controlling the fuel fiowthrough said conduit; a stop movable relative to said throttle valveinto and out of a position and operative at least in said position tolimit the opening movement of said throttle valve; a first chamber; anevacuated second chamber; a flexible diaphragm dividing said firstchamber from said second chamber and connected to said stop; apressure-tapping from the discharge of said compressor to said firstchamber whereby said diaphragm is loaded by a resultant pressure loadproportional to the absolute discharge pressure of said compressor; anda loading device arranged to load said diaphragm with a selected loadtowards said first chamber; whereby said stop moves out of said positionwhen said resultant pressure load exceeds said selected load and intosaid position when the resultant pressure load falls below said selectedload, and to transmit to said diaphragm the opening load applied to saidthrottle; and means to apply to said diaphragm a load equal in magnitudeand opposite in direction to said opening load.

14. A gas-turbine engine having a rotor and a fuel-supply system; aconduit in said system; a throttle valve for controlling the fuel flowthrough said conduit; a constant volume pump; a driving connectionbetween said pump and said rotor, whereby said pump is driven at a speedproportional to that of said rotor; a dischargeconduit from said pump; avariable restriction in said discharge-conduit; a fixed restriction insaid discharge conduit between said variable restriction and saidconstant volume pump; a first chamber, a second chamber and a firstflexible diaphragm dividing said first chamber from said second chamber;a third chamber; a second flexible diaphragm, of the same area as andcoaxial with said first diaphragm, dividing said second chamber fromsaid third chamber and connected to said throttle valve; pressuretappings from said discharge-conduit upstream of said fixed restrictionto said first chamber, from said discharge conduit downstream of saidvariable restrictive to said second chamber, and from said dischargeconduit between said fixed restriction and said variable restriction tosaid third chamber, whereby said first diaphragm is loaded by a firstresultant pressure load proportional to the pressure drop across bothsaid restrictions and said second diaphragm is loaded by a secondresultant pressure load proportional to the pressure drop across saidvariable restriction, said second diaphragm being connected to saidthrottle valve so that increase of said second resultant pressure loadcloses said throttle valve; a stop in said second chamber carried bysaid first diaphragm; a loading device loading said first diaphragm witha selected load towards said first chamber; a resilient loading deviceabutting between said first and second diaphragms; and a co-operating'abutment carried by said second diaphragm and arranged to engage withsaid stop and to become disengaged therefrom by movement of said stop asa result of increase in said first resultant pressure load to a firstpreselected value greater than said selected load, and to be engagedtherewith when said first resultant pressure load is less than saidselected load and said second resultant pressure load is less than asecond preselected value.

15. A gas-turbine engine as claimed in claim 14 further comprising meansto maintain the pressure drop across said throtle valve proportional tothe square of the speed of the rotor.

16. A gas-turbine engine having a rotor and a fuel-supply system; aconduit in said system; a throttle valve for controlling the fuel fiowthrough said conduit; a constant volume pump; a driving connectionbetween said pump and said rotor whereby said pump is driven at a speedproportional to that of said rotor; at dischargeconduit from said pump;a fixed restriction in z N sa d scharee oonduit; a arisble'restdotionaid di charg nduit between said fi ed r s r o n. n sa d constant vo umPump; a fir chamber, a second chamber and a first flexible diaph d i i dfirst hamber f om. ai ec d hamber: a third cham er a. r h m e d a nd. flxible h a m. axial with and of the same effective area as said first aragm d di g a h rd. ha b f m d f h chamb r; a d cond nd h r chambersbeing located between said first and se ond d ap agm; p ssure ta piesfromsai disc rg -co du t ups r am o said r able restriction to saidfirst chamberv and. saidfourth chamber, from said discharge-conduitdownstream of said fixed restriction to said second chamber, and fromsaid. discharge Conduit between said fixed restriction and said variablerestriction to said third chamber whereby said first d a h is oaded by as r su ant pressur load proportional to the pressure drop across bothsaid restrictionsand said second diaphragm is loaded by a secondresultant pressure load pro-,- portional to the pressure drop, acrosssaid variable restriction; a stop carried by said first diaphragm andlocated between said first diaphragm and said second diaphragm; aloading device loading said first diaphragm with a selected load towardssaid first chamber; a first resilient loading device loadin said firstdiaphragm with a first resilient load towards Said first chamber; asecond resilient loading device loading said second diaphragm towardssaid fourth chamber with a second resilient loadequal toand of the samerate as said first resilient load; an operative connection between saidsecond diaphragm and said throttle valve-arranged so that movement ofsaid second diaphragm, as a result of increase of said second resultantpressure load, closes said throttle valve; and a co-operating abutmentcarried by said second diaphragm and arranged to engage with said stopand to become disengaged therefromby movement of said stop as a resultof; increasein said first resultant pressure load to a firstpreselectedvalue greater than said selected load, and-to be engaged therewith whensaid first resultant pressure load is less than said selected load andsaid second resultant pressure load is less than a second preselectedvalue.

17. A gas-turbine engine havinga rotor and a ue supp ysystem; a ondu t nsaid.- ys em; a throttle valve for controlling the fuel. flow throughsaid conduit; a, driving; connection bewe n a d pu p and said rotor wheeby-said pump is driven at a speed proportional to that of said rotor; adischarge-conduiti-rom said pump; a first fixed restriction in saiddischarge-conduit; a second fixed restriction in said discharge condulbetween said first fixed, restriction and-said constant volume pump; afirst chamber, a secand chamber and a first, flexible diaphragmdividing. said first chamber from said second chamber; a third chamber;asecond flexiblediaphragm of the same area. as and coaxial with saidfirst diaphragm, dividing saidsecondcham her from said third chamber;pressureztappings from said discharge-conduit. upstream of said secondfixed restriction to said first chamber,

from. said discharge-conduit. downstream of said first fixedrestriction: to said second chambenand from said discharge conduitbetween said first fixed restriction and said second fixed restrictionto aid third chamber, whereby said'first diaphragmis loaded with a firstresultant pressure see s 22, v load proportional t the pressure dropacross both said fixed restrictions and said second diaphragm is loadedwith a second resultant pres.- sure load proportional to th pressuredrop. across said first fixed restriction; a stop in said second chambercarried by said first diaphragm; a load-. ing device loading said firstdiaphragm with a selected load towards said first chamber; a, firstspring loading said first diaphragm with a first resilient load towardssaid first chamber, and abutting a first movable abutment; a secondspring equal to and of the same rate as said first spring loading saidsecond diaphragm with a second resilient load towards said. thirdchamber, and abutting av second movable abutment; means to move bothsaid movable, abutments simultaneously and equally so that said firstand sec.- ond resilient loads are adjustable but maintained equal; anoperativeconnection between Said sec..- nd diaphr and said throttlevalve arran ed so that movement of said. second diaphragm, as a resultof increase of said second resultant pressure load, closes said throttlevalve; and a 0,- operating abutment carried by said second diaphragm andarranged to engag with saidstop and to become disengaged therefrombymovement of said stop as a result, of increase in said first resultantpressure load to a. first preselected value greater than saidselectedload, and to. be engaged therewith when said first, resultantpressure load is less than said selected load. and said second resultantpressure: loadis lessthan a second preselected value,

18. A gas-turbine engine havinga compressor, a rotor-,and a fuel supply'system; a conduit in said system; a throttle valve for controlling thefuel fiow through said conduit; a constant volume pump; 7 a driving,connection between said pump and said rotor whereby said pump is drivenat a speed proportional to that of said rotor; a discharge-conduit fromsaid pump; a variable restriction in said discharge-conduit; a firstchamber; a first evacuatedcapsule in. said first chamber; a secondchamber; asecond evacuated capsule in saidsecond chamber; a lever; afirst rod carried for movement with the free end of said first evacuatedcapsule and pivotally connected to said lever; a second rod carried formovement with the free end of said second evacuated capsule andpivotally, connectedto said lever; a fixed fulcrum forsaicl leverbetweenthe connections of said first rod and said second rod; a thirdchamber, a. fourth chamber and a first flexible diaphragmdividingsaidthird' chamber from said fourth chamber; a fifth chamber, asixth chamber and a second flexible diaphragm dividing said fifthchamber from said sixth chamber; pressure'tappings from the discharge ofsaid compressor to said first chamber, from the inlet of said compressorto said second cham her, from said discharge eonduit upstream of saidvariable restriction to said'third chamber and said sixthchambenandifrom said dischargeconduit downstreamof said variable restriction tosaid fourth chamber and said fifth: chamber; whereby said lever isloaded: with aresultant pressure moment proportional to :the compressionratio of said. compressor;- said first diaphragm is loaded with afirstresultantpressure 23 phragm; a stop carried for movement with said firstdiaphragm; a selected moment loading said lever in the same sense asressure in said second chamber; a first resilient loading device loadingsaid first diaphragm with a first resilient load towards said thirdchamber; a second resilient loading device loading said second diaphragmwith a second resilient load towards said sixth chamber; a secondoperative connection interconnecting said second diaphragm and saidthrottle valve, and arranged so that movement of said second diaphragmdue to increase in said second resultant pressure load closes saidthrottle valve; and a co-operating abutment connected with said seconddiaphragm and arranged to engage said stop and to become disengagedtherefrom by movement of said stop as a result of increase of saidresultant pressure moment to a first preselected value greater than saidselected moment, and to be engaged therewith when said resultantpressure moment is less than said selected moment and said secondresultant pressure load is less than a second preselected value; saidthird, fourth, fifth and sixth chambers and said first and secondoperative connections being so arranged, and said first and seconddiaphragms and said first and second resilient loads beingso dimensionedthat, when said stop and said co-operating abutment are engaged, saidfirst and second resultant pressure loads and said first and secondresilient loads balance each other, the position of said stop beingdetermined solely by said resultant pressure moment and said selectedmoment.

19. In a fuel system for gas turbine engines and the like having fuelinjectors and a fuel supply conduit to the fuel injectors, a valvememberin said conduit, normally-operative control means to move saidvalve member to control the supply of fuel to the injectors, abutmentmeans rigidly connected to said valve member to move therewith, a stopadjustable independently of said valve member and including normallydisengaged cooperating abutment means to engage the first said abutmentmeans to define the limit of normal movement of said valve member in thesense of increasing the flow of fuel, and adjusting means responsivesolely to an operating variable which is at least in part dependent onthe speed of the engine, the adjusting means being rigidly connected tosaid stop, whereby the position of the stop is dependent solely on thevalue of said variable when said cooperating abutment means is inengagement with the first said abutment means.

20. In a fuel system for gas turbine engines and the like having fuelinjectors and a fuel supply conduit to the fuel injectors, a valvemember in said conduit, normally-operative control means to move saidvalve member to control the supply of fuel through the injectors,abutment means connected to said valve member, an adjustable stopincluding co-operating abutment means to engage the first said abutmentmeans, fluid-pressure-sensitive adjusting means connected to said stopand subjected to a pressure difference dependent on an operatingvariable which is at least in part dependent on the speed of the engine,and resilient means to load said adjusting means in opposition to saidfluid pressure, whereby the position of the stop is adjusted when thevalue of said operating variable varies.

21. In a fuel system for gas turbine engines and the like having fuelinjectors and a fuel supply conduit. to the fuel injectors, a valvemember in said conduit, normally-operative control means to move saidvalve member to control the supply of fuel to the injectors, abutmentmeans rigidly connected to said valve member to move therewith, a stopadjustable independent of said valve member and including normallydisengaged cooperating abutment means to engage the first said abutmentmeans to define the limit of normal movement of said valve member in thesense of increasing the flow of fuel, and speed-responsive adjustingmeans rigidly connected to said stop, whereby the position of the stopis dependent on the speed of the engine when said cooperating abutmentmeans is in engagement with the first said abutment means.

22. In a fuel system for gas turbine engines and the like having fuelinjectors and a fuel supply conduit to the fuel injectors, a valvemember in said conduit, normally-operative speed governor control meansto move said valve member to control the supply of fuel to theinjectors, abutment means connected to said valve member, an adjustablestop including co-operating abutment means to engage the first saidabutment means to define the limit of said normal movement in the senseof increasing the flow of fuel, fiuid-pressure-sensitive adjusting meansconnected to said stop and subjected to a pressure difference dependentsolely on an operating variable which is at least in part dependent onthe speed of the engine, and resilient means connected to said adjustingmeans to oppose said fluid pressure, whereby the position of the stop isadjusted when a selected value of said operating variable is passedthrough.

23. For use in a throttle-valve-controlled fuelsupply system in gasturbine engines, normallyoperative control means to move said throttlevalve to control the supply of fuel to the engine, abutment meansrigidly connected to said throttle valve to move therewith, a stopadjustable independently of said valve member and including normallydisengaged cooperating abutment means to engage the first said abutmentmeans to define the limit of normal movement of said valve member in thesense of increasing the flow of fuel, and adjusting means rigidlyconnected to said stop and responsive solely to an operating variablewhich is at least in part dependent on the speed of the engine, wherebythe position of the stop is dependent solely on the value of saidvariable when said cooperating abutment means is in engagement with thefirst said abutment means.

24. For use in a throttle-valve-controlled fuelsupply system in gasturbine engines, normallyoperative control means to move said throttlevalve, abutment means connected to said throttle valve, an adjustablestop including co-operating abutment means to engage the first saidabutment means to define the limit of said normal movement in the senseof increasing the flow of fuel, operating variable responsive adjustingmeans connected to said stop to load it solely in dependence on anoperating variable which is at least in part dependent on the speed ofthe engine, and pre-stressed resilient means to load said adjustingmeans in opposition to said operating-variable-responsive means, wherebythe load due to the operating-variable-responsive means overcomes theprestressed resilient load and causes the stop to be adjusted to permitgreater opening movement of the valve when said operating variablepasses through a selected value during acceleration of the engine, andwhereby return movement of the stop in the opposite direction is causedwhen said selected value is passed through during deceleration of theengine.

KENNETH ROY DAVIES. KARL HERBSTRITT.

References Cited in the file of this patent UNITED STATES PATENTS NumberNumber Number Name Date Sdille Dec. 9, 1947 Chamberlin et a1. June 21,1949 Nicolls Sept. 6, 1949 Ray Nov. 29, 1949 Mock Jan. 1, 1952 FOREIGNPATENTS Country Date Great Britain June 4, 1935 Great Britain Mar. 24,1944

